Gold particles to treat tumours

May 12, 2009

MIT (Massachusetts Institute of Technology) researchers have been working on a difficult problem. Heat is an effective weapon against tumour cells, but the difficulty has been to heat patients’ tumours without damaging nearby tissues. The solution turns out be golden – in fact tiny gold particles that can home in on the tumour, and then, by absorbing energy from near-infrared light and emitting it as heat, destroy them with virtually no side effects.

Gold nanoparticles can absorb different frequencies of light, depending on their shape. Rod-shaped particles, such as those used in the research, absorb light at near-infrared frequency; this light heats the rods but passes harmlessly through human tissue. Once the nanorods are injected, they disperse uniformly throughout the bloodstream and then into blood vessels located near tumours which have tiny pores just large enough for the nanorods to enter. The nanorods then accumulate in the tumours, and within three days, the liver and spleen clear any that don’t reach the tumour itself.

During a single exposure to a near-infrared laser, the nanorods heat up to 70 degrees Celsius, hot enough to kill tumour cells, and at a lower temperature they weaken tumour cells enough to enhance the effectiveness of existing chemotherapy. Another use for this treatment is to kill tumour cells left behind after surgery. The nanorods can be more than 1,000 times more precise than a surgeon’s scalpel, and so could potentially remove residual cells the surgeon can’t get at.

The statistics on cancer are daunting. There are currently around 7 million people worldwide diagnosed and that number is projected to grow to 15 million by 2020. As the majority are treated with a combination of chemotherapy and/or radiation, they are subject to debilitating side effects because of the difficult in accurately targeting tumour tissue. At present, 99 percent of chemotherapy drugs are estimated to not reach the tumour, but the gold nanorods can specifically focus heat with a much greater accuracy to destroy the tumour.